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Nationwide Desert Highway Assessment: a Case Study in China

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Nationwide Desert Highway Assessment: a Case Study in China Int. J. Environ. Res. Public Health 2011, 8, 2734-2746; doi:10.3390/ijerph8072734 OPEN ACCESS International Journal of Environmental Research and Public Health ISSN 1660-4601 www.mdpi.com/journal/ijerph Article Nationwide Desert Highway Assessment: A Case Study in China Xuesong Mao *, Fuchun Wang and Binggang Wang Key Laboratory for Special Area Highway Engineering of Ministry of Education, Chang’an University, Xi’an 710064, China; E-Mails: [email protected] (F.W.); [email protected] (B.W.) * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel.: +86-29-82334869; Fax: +86-29-82334869. Received: 20 May 2011; in revised form: 13 June 2011 / Accepted: 26 June 2011 / Published: 30 June 2011 Abstract: The natural environment affects the construction of desert highways. Conversely, highway construction affects the natural environment and puts the ecological environment at a disadvantage. To satisfy the variety and hierarchy of desert highway construction and discover the spatio-temporal distribution of the natural environment and its effect on highway construction engineering, an assessment of the natural regional divisions of desert highways in China is carried out for the first time. Based on the general principles and method for the natural region division, the principles, method and index system for desert highway assessment is put forward by combining the desert highway construction features and the azonal differentiation law. The index system combines the dominant indicator and four auxiliary indicators. The dominant indicator is defined by the desert’s comprehensive state index and the auxiliary indicators include the sand dune height, the blown sand strength, the vegetation coverage ratio and the annual average temperature difference. First the region is divided according to the dominant indicator. Then the region boundaries are amended according to the four auxiliary indicators. Finally the natural region division map for desert highway assessment is presented. The Chinese desert highways can be divided into three sections: the east medium effect region, the middle medium-severe effect region, and the west slight-medium effect region. The natural region division map effectively paves the way for the route planning, design, construction, maintenance and ongoing management of desert highways, and further helps environmental protection. Int. J. Environ. Res. Public Health 2011, 8 2735 Keywords: highway engineering; desert assessment; index system; environmental protection 1. Introduction There are about 7,900 kilometers of desert highways in China, mainly distributed in the Xinjiang Ugur Autonomous Region, Ningxia Hui Autonomous Region, Neimengu Autonomous Region and Gansu Province and some other areas. The differences between desert highways and general highways are due to the effects of the arid climate, the wind sand and the temperature on highway construction engineering. Another difference is the shortage of suitable filling materials such as soils and stones for highway construction in desert regions, which makes it more difficult to construct a desert highway. A highway exists in the natural environment as a structure. The elements of the natural environment affect the highway construction engineering. At another hand, the construction affects the natural environment and puts the ecological environment at a disadvantage. Especially in desert regions the highways can always be blocked by the encroachment of sand dunes [Figure 1(a)], and the highway traffic can cause severe wind erosion of grassland soils [Figure 1(b)]. To satisfy the variety and hierarchy of the highway construction and discover the spatio-temporal distribution of the desert natural environment and its effects on highway construction, a desert highway assessment should be carried out, which will effectively pave the way for route planning, design, construction, maintenance and subsequent management of desert highways, and help formulate standards. Figure 1. Interactive effects between highway engineering and the natural environment. (a) highway blocked by dune encroachment (b) Severe wind erosion of grassland soil due to traffic Desert highway assessment studies have been going on for many years. The earliest desert assessment can be dated back to Lamprey’s research in central western Sudan, when he introduced the desert encroachment theory [1], which laid the groundwork for providing a process for measuring the desertification problem. A provisional methodology for assessment and mapping of desertification was formulated [2,3] and is now used for local and regional assessment and mapping [4,5]. Most of the studies assess the desert based on the desert topography, vegetation coverage and wind erosion. The desert is divided into two kinds (fixed and mobile) or three kinds (fixed, part fixed or mobile), according to the extent of the activity of the sand dunes. China began a nationwide desertification assessment in the mid-1980s. Historically, China had focused on sandy desertification, which is caused by wind erosion [6]. This classification method was based on geo-morphological changes caused by Int. J. Environ. Res. Public Health 2011, 8 2736 blowing sand (such as sand dunes and sand mound formations, sand cover, and surface coarseness), the percentage of change in relation to the total area, and the annual rate of increase of desertified land. These classifications had been broadly used in sandy desertification assessment [7]. Based on hundreds of expert questionnaires, sandy desertification intensities were classified as slight, medium, severe, or extremely severe [8]. The main assessment indicators were bare sand ratio, vegetation coverage ratio, and soil texture, and the importance of each indicator was calculated by the Delphi weighted method. However a desert highway assessment that comprehensively describes the natural highway distribution or single local highway distribution has not been reported until now at home or abroad. With the increase in highway construction, especially as a result of the Western Development Plan of China, highway construction in the desert regions had accelerated considerably and the highway mileage has increased yearly. Li Bin had put forward the idea of desert highway assessment in China. He designed the indicators as the moisture coefficient and aimed to determine the differences of the highway subgrade protective level in desert regions [9]. However, he only put forward the theory and the natural region division map for desert highway assessment was not drawn out. His studies were rough and could not be applied to actual highway construction. This paper borrows the idea of desert assessment method. Based on the general principle and method for the regional division, the principles, method and index system for the desert highway assessment are put forward by combining the desert highway construction and the azonal differentiation law. The method of combining both one dominant indicator and four auxiliary indicators is applied to divide the desert highway region distribution in China for the first time. 2．Principle and Method for Desert Highway Assessment 2.1. Principles of Desert Highway Assessment (1) Service principle: Desert highway assessment will serve the highway engineer in China. The objective of the assessment is clear, namely to provide the basic science data for balancing the highway construction and the protection of the natural environmental, to further promote the sustainable development of desert regions [10]. (2) Practicability principle: The desert highway assessment process can comprehensively reflect the natural characteristics. It studies the effect of natural environment factors on the highway construction from the viewpoint of a real highway engineer. At the same time it synthesizes the differences between desert highways and general highways with respect to the route design, subgrade, pavement, and protection works. (3) Dialectical principle: All the factors, such as the sand physiognomy, sand strength, temperature annual difference, and the vegetation will affect the desert highway construction. They are related and correlative. The desert highway assessment divides the nationwide desert highway regions in China according to their similarity and the differences between natural factors. The regional divisions should not conflict with each other. (4) Absolute consistency: Every natural unit forms along history little by little. The desert highway assessment should discuss the reason and process of the desert region and pave the way for regional division. Only under the absolute consistency principle, can the correlative consistency of the divided or united desert unit be guaranteed during the highway region division. Int. J. Environ. Res. Public Health 2011, 8 2737 (5) Relative consistency: The relative consistency requires that the internal consistency should be maintained for the desert highway division. Different region unit levels are different in their consistency. (6) Combination of comprehensive and dominant factors: Any desert region is combined with several natural geological factors. The desert highway assessment should pay attention to analyze their modes of interaction, to process these factors and to recognize the real discipline of the regional differences. At the same time, the dominant factor should be distinguished among all other factors. This principle is balanced between the comprehensive and dominant factor. (7) Similar characteristics
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